Carver County Water Management, by Madeline Seveland
Similar to engineers, lawyers and many other professionals, water resource scientists have a lingo all their own that they use to convey water messages.
However, many terms are not familiar to most citizens if they are, they mean different things.
This column will focus in introducing you to a few of the most common terms used when discussing pollution in surface waters. Surface waters are lakes, rivers and wetlands.
Ever see a muddy looking river? Then you’ve likely seen a river impaired by Turbidity. Turbidity in water is caused by suspended soil, algae and other particles that scatter and absorb sunlight passing through the water making the water appear cloudy. Excessive turbidity makes it difficult for fish and other aquatic species to find food, use their gills (they get clogged with particles) and navigate through the water. It can also cover spawning beds.
Sediment is one of the particles that cause turbidity. Sediment is dirt; often dirt from roads or eroded soil. Sediment causes many of the same problems as turbidity. In addition, contaminants like oil, pesticides, nutrients and bacteria all can bind very tightly to soil particles. Thus, when you have sediment washing into lakes and rivers you often are getting more pollution than just too much dirt.
Nutrients are very familiar to those who garden a lot. They are plant food. Mostly when talking about nutrients water scientists focus on nitrogen and phosphorus. These nutrients help our plants grow, but if too much gets into waters is they cause another type of plant growth – ALGAE! Algae are small free-floating water plants that turn water green, slimy and smelly. Algae can grow quickly, and when they die they use up all the oxygen in the water. Oxygen is necessary for many aquatic species thus these algae die offs cause fish kills and other problems.
Fecal Coliform is a type of bacteria, specifically bacteria that can be found in the small intestines of warm-blooded animals. Although fecal coliform bacteria are generally not harmful themselves, they indicate the possible presence of pathogenic (disease causing) bacteria, viruses and protozoans that also live in human and animal digestive systems.
Fecal coliform are used as indicator bacteria. Their presence indicates there may be sewage flowing into the lake or river from on-site septic systems, and domestic and wild animal manure/waste.
A common type of fecal coliform bacteria that almost everyone has heard of is E. coli. Although most E. coli are harmless, yet there is one strain, O157, that produces a powerful toxin that can cause severe illness. This is the strain we hear about the most in news items.
Total Maximum Daily Load or TMDL is the maximum amount of pollution a river or lake can take and still maintain a healthy state (does not exceed water quality standards). Each water body has an allowable daily pollutant load limit associated with it. For example, a shallow lake cannot receive any more than 40